1. Field of the Invention
The present invention relates to light-sensitive compositions and more particularly to light-sensitive compositions which permit the reduction in drying load and are quick-drying compositions suitable for continuous coating.
2. Description of the Prior Art
Light-sensitive compositions have, in general, been used in a manner that they are coated on a support such as surface treated aluminum plates, paper, plastics or SiO.sub.2 /Si wafer in the form of solution or dispersion in an organic solvent and then are dried. When the light-sensitive compositions are coated on a support and then are dried, it is quite important to select organic solvents to be used in order to sufficiently take advantages of the properties of the light-sensitive composition and from viewpoints of economy and safety.
On the other hand, if it is intended to industrially produce presensitized plates (hereunder referred to as "PS plate(s)" among others, it is quite effective to continuously coat a wet support with a light-sensitive composition and dry the composition coated, while continuously conveying the web support. However, in such case, the drying procedure should be carried out in a short period of time for the purposes of eliminating the use of a large and complicated drying installation and saving cost. For this purpose, it is required that solvents having a boiling point of from low range to middle range are used in a large amount. However, in such case, it was found that important properties of PS plates such as development latitude, developing capability (i.e., the area of a PS plate which can be developed without any appreciable decrease in sensitivity by a unit of developer), film strength, ink receptivity or the like are largely impaired or extremely lowered when a positive-working light-sensitive composition is coated and dried with utilizing solvent of a boiling point falling within the above range.
In addition, the use of a solvent combined with one having a high boiling point (e.g., 210.degree. C. or more) is also known. For instance, Japanese Patent Appln. (opened to public inspection, hereunder referred to as "OPI" for simplicity) No. 60-24545 discloses a positive-working light-sensitive composition obtained by dissolving an alkali-soluble novolak resin and a 1,2-quinonediazide compound in a mixed solvent comprising (A) an organic solvent of a boiling point of from 60.degree. to 170.degree. C. and (B) an organic solvent of a boiling point of from 180.degree. to 350.degree. C. in a ratio, (A)/(B), of from 1 to 99 (weight ratio). This invention relates to a positive-working light-sensitive resin composition having a quite low striation, obtained by utilizing an alkali-soluble novolak resin as a major component and coating it on a support such as a silicon wafer according to spin coating technique. In other words, the invention intends to control the degree of drying during spin coating, by the addition of a high boiling point solvent Therefore, the use of such kind of composition requires a drying process over an extremely long period of time.